Orthostatic blood pressure control and ageing.

ABSTRACT

Reflex haemodynamic responses to orthostatic stress are attenuated with ageing, the extent of attenuation increasing with advancing age. In 15-20% of individuals aged > 65 years, the attenuation may be so marked that there is an excessive fall of blood pressure (BP) on assumption of the upright posture, sufficient on occasions to cause symptomatic cerebral hypoperfusion--this is known as 'ageing-related' orthostatic hypotension (AOH), a major risk factor for morbidity and mortality. Comparison of the cardiovascular responses to a variety of physiological and pharmacological stresses in healthy young and elderly subjects and in those with AOH suggests that the predominant site of the ageing-related change in cardiovascular reflex function is in the central connections of the arterial baroreflex, affecting particularly the BP buffering response. There is no evidence for ageing-related impairment of the efferent limb of the baroreflex, i.e. there is no significant ageing change in sympathetic vasomotor function or cardiac drive. Ageing-related impairment of baroreflex function also does not appear to result from either attenuation of arterial compliance or the presence of systolic hypertension, despite the epidemiological association between systolic hypertension and AOH. Better understanding of this important problem has the potential to improve the health of all elderly people.